.TH std::piecewise_linear_distribution 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::piecewise_linear_distribution \- std::piecewise_linear_distribution

.SH Synopsis
   Defined in header <random>
   template< class RealType = double >   \fI(since C++11)\fP
   class piecewise_linear_distribution;

   std::piecewise_linear_distribution produces random floating-point numbers, which are
   distributed according to a linear probability density function within each of the
   several subintervals \\(\\small{[b_i, b_{i+1})}\\)[b
   i, b
   i+1). The distribution is such that the probability density at each interval
   boundary is exactly the predefined value \\(\\small{p_i}\\)p
   i.

   The probability density for any \\(\\small{ b_i \\le x < b_{i+1} }\\)b
   i≤x<b
   i+1 is \\(\\small{p_i\\frac{b_{i+1}-x}{b_{i+1}-b_i} + p_{i+1}\\frac{x-b_i}{b_{i+1}-b_i}
   }\\)p
   i

   b
   i+1-x
   b
   i+1-b
   i

   + p
   i+1

   x-b
   i
   b
   i+1-b
   i

   , where probability densities at interval boundaries \\(\\small{p_k}\\)p
   k are calculated as \\(\\small{w_k/S}\\)w
   k/S where \\(\\small{S}\\)S is the sum of all \\(\\small{\\frac{1}{2}(w_k +
   w_{k+1})(b_{k+1} - b_k)}\\)

   1
   2

   (w
   k+w
   k+1)(b
   k+1−b
   k).

   The set of interval boundaries \\(\\small{b_i}\\)b
   i and the set of weights at boundaries \\(\\small{w_i}\\)w
   i are the parameters of this distribution.

   std::piecewise_linear_distribution satisfies all requirements of
   RandomNumberDistribution.

.SH Template parameters

   RealType - The result type generated by the generator. The effect is undefined if
              this is not one of float, double, or long double.

.SH Member types

   Member type         Definition
   result_type \fI(C++11)\fP RealType
   param_type \fI(C++11)\fP  the type of the parameter set, see RandomNumberDistribution.

.SH Member functions

   constructor   constructs new distribution
   \fI(C++11)\fP       \fI(public member function)\fP
   reset         resets the internal state of the distribution
   \fI(C++11)\fP       \fI(public member function)\fP
.SH Generation
   operator()    generates the next random number in the distribution
   \fI(C++11)\fP       \fI(public member function)\fP
.SH Characteristics
   intervals     returns the distribution parameters
   densities     \fI(public member function)\fP
   \fI(C++11)\fP
   param         gets or sets the distribution parameter object
   \fI(C++11)\fP       \fI(public member function)\fP
   min           returns the minimum potentially generated value
   \fI(C++11)\fP       \fI(public member function)\fP
   max           returns the maximum potentially generated value
   \fI(C++11)\fP       \fI(public member function)\fP

.SH Non-member functions

   operator==
   operator!=                compares two distribution objects
   \fI(C++11)\fP                   \fI(function)\fP
   \fI(C++11)\fP(removed in C++20)
   operator<<                performs stream input and output on pseudo-random number
   operator>>                distribution
   \fI(C++11)\fP                   \fI(function template)\fP

.SH Example


// Run this code

 #include <iomanip>
 #include <iostream>
 #include <map>
 #include <random>
 #include <string>

 int main()
 {
     std::random_device rd;
     std::mt19937 gen{rd()};
     // increase the probability from 0 to 5
     // remain flat from 5 to 10
     // decrease from 10 to 15 at the same rate
     std::vector<double> i{0, 5, 10, 15};
     std::vector<double> w{0, 1, 1, 0};
     std::piecewise_linear_distribution<> d{i.begin(), i.end(), w.begin()};

     std::map<int, int> hist;
     for (int n{}; n < 1e4; ++n)
         ++hist[d(gen)];

     for (auto [x, y] : hist)
         std::cout << std::setw(2) << std::setfill('0') << x
                   << ' ' << std::string(y / 100, '*') << '\\n';
 }

.SH Possible output:

 00 *
 01 ***
 02 ****
 03 ******
 04 *********
 05 *********
 06 *********
 07 **********
 08 *********
 09 **********
 10 *********
 11 *******
 12 ****
 13 ***
 14 *
